Hitherto, organic acids or their salts and glycol series pastes have been principally used as an electrolyte for electrolytic capacitor in the general purposes. The latest expansion of utilization for the electronic instruments requires more improvement and advancement in reliability and performance of the capacitor entailing the undesired problem of the presense of water in the paste and as a result an electrolyte using an aprotic solvent in place of organic acid and its salt and glycol paste has begun to receive attention.
The greatest subject of attention of the aprotic solvent system electrolyte is how to obtain an electrolyte of high conductivity and to achieve this by the use of an organic carboxylic acid or its salt which is well soluble in the aprotic solvent and has a high degree of disassociation has been the subject of much research which has not yet been successful. To solve the matter and obtain a high conductivity a solvent which produces water resulting from the reaction between acids and alcohols or glycols and even water is incorporated into the aprotic solvent, but with still insufficient conductivity, increments of water and solute contents with poor reliability at the elevated temperature as disclosed in the Japanese patent publications No. 55-3989, 57-56763, 58-32769 and the U.S. Pat. No. 4,117,531.
After extensive researches and studies concerned with obtaining an electrolyte which is a substantially nonaqueous system electrolyte and which has a high conductivity with use of an aprotic solvent but without using any solvent which forms water in reaction between acids and alcohols with glycols, it has been discovered that an organic amine salt of tetrafluoroborate has a high solubility in the aprotic solvent with an enhanced releasability and provides a high conductivity.